For the rigid polyurethane foam used in metal composite roof panels, tensile and compression tests were carried out in its foaming and coating directions respectively, and basic mechanical parameters in those characteristic directions were obtained. The results reveal that the rigid polyurethane foam cannot be regarded as isotropic material due to the differences of the tensile and compressive behaviors between the foaming direction and the coating direction. Brittle fracture occurs in the tensile testing. However, there are yield platform and lack of damage in the compressive case. The mechanical parameters of the rigid polyurethane foam in the foaming direction and the coating direction are also different. The tensile and compressive elastic moduli in the foaming direction are only half of those in the coating direction, while the tensile ultimate strength and compression yield strength in the foaming direction are also less than that in the coating direction. Based on the data in test, a transversely isotropic constitutive model suitable for the rigid polyurethane foam is suggested and main parameters of the model are fitted in the end.